tailieunhanh - Encyclopedia of Smart Materials (Vols 1 and 2) - M. Schwartz (2002) WW Part 4

Tham khảo tài liệu 'encyclopedia of smart materials (vols 1 and 2) - m. schwartz (2002) ww part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Instantaneous formation of CS PEO-PPO nanoparticles Figure 6. Scheme for preparing CS nanoparticles. porosity of the matrix of the freeze-dried hydrogel compared to that of the air-dried hydrogel 23 . The ionic interaction between the positively charged amino groups of chitosan and negatively charged counterion of tripolyphosphate TPP MW 4000 results in polyelectrolyte complex formation and thus allows the formation of beads in very mild conditions. So chitosan nanoparticles can be prepared by ionic gelation with the counterion TPP 24 . The particle size depends on both the chitosan and TPP concentrations. The minimum size 260 nm has been obtained. The PEO or PEO-PPO block polymer Synperonic 1C1 Iberica Spain can be incorporated into chitosan nanoparticles by dissolving these copolymers in the chitosan solution either before or after adding the ionic cross-linker TPP Fig. 6 . TEM observation reveals that the chitosan nanoparticles have a solid and consistent structure whereas chitosan PEO-PPO nanoparticles have a compact core which is surrounded by a thin but fluffy coat presumably composed of amphophilic PEO-PPO copolymer 25 . Here the presence of PEO-PPO within the chitosan nanoparticles can mask the ammonium group of chitosan by a steric effect thus hindering the attachment of the BSA isoelectric point pH . These hydrophilic chitosan ethylene oxide-propylene oxide block copolymer nanoparticles are very promising matrices for administering therapeutic proteins and other macromolecules that are susceptible to interaction with chitosan . genes or oligonucleotides 26 . Mucoadhesive drug delivery systems can easily be combined with auxiliary agents such as enzyme inhibitors. Chitosan and EDAC 1-ethyl-3- 3-dimethylamino-propyl carbodimine hydrochloride form chitosan-EDAC conjugates 10 mL of 1 chitosan HCl EDAC and an amount of EDAC that ranges from to g at pH . The chitosan-EDAC conjugates offers several creased understanding of molecular .